Agoraphobia is based on a fear of situations grouped into five categories. These categories are:

• public transportation
• open spaces
• enclosed public spaces
• crowds or standing in line
• being outside of the home in general

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The fear or anxiety must occur in two of the five situations to meet the current criteria for agoraphobia. According to the DSM-5, if the individual fears only one situation, the specific phobia is the diagnosis. Agoraphobia also differs from a specific phobia in terms of the feared consequences.

If the situation is feared because of expected anxiety or panic responses alone, it falls into the category of agoraphobia. If the situation is feared for other reasons, then it is more likely a specific phobia. Agoraphobia is usually defined as a part of panic disorder. The lifetime prevalence rate for agoraphobia with panic disorder is 1.1 percent.

Agoraphobia has recently been redefined as a separate disorder that can occur with or without panic disorder. The prevalence of agoraphobia without panic disorder is about 0.8 percent. In another survey of adolescents and young adults, however, that did not follow the DSM-IV hierarchy rules requiring agoraphobia to be diagnosed within the context of panic disorder, the incidence of agoraphobia was 5.3 percent. When the DSM-IV rules were applied, that number dropped to 0.6 percent.

Older adults

Compared to adolescents and young adults, the prevalence of agoraphobia among elderly people is somewhat lower. In one study, the prevalence of agoraphobia in adults over 55 was 0.61 percent. A bivariate analysis showed the disorder as more common in younger people, women, and those widowed or divorced.

Risk factors and comorbidity

A number of risk factors are associated with agoraphobia. Those include:

• panic disorder
• younger age
• female gender

The rate of comorbidity of agoraphobia with other anxiety disorders ranges from 49 to 60 percent, and with depressive disorders it is 33.1 to 52 percent.

Significant comorbid conditions include:

• specific phobia: 73.7 to 75.2 percent
• social phobia: 66.5 percent
• generalized anxiety disorder: 15 to 31.9 percent
• posttraumatic stress disorder: 24.2 to 39.6 percent
• major depressive disorder: 38.5 to 48.7 percent
• bipolar disorder: 15.5 to 33 percent
• substance use disorders: 31.4 to 37.3 percent

Course

The median age of onset for agoraphobia is 20 years. Onset before the age of 55 is most common. The disorder typically does not remit without treatment. In a study following subjects for ten years, agoraphobia without panic attacks was one of the most persistent disorders, with rare complete remission.

Causes of agoraphobia

Biological, psychological and environmental factors are believed to contribute to agoraphobia. Studies have shown some familial clustering of agoraphobia. Heritability of agoraphobia is estimated at between 48 and 61 percent, meaning the genetic contribution is moderate with contributions from environmental factors being influential.

Personality factors influencing agoraphobia include introversion/extroversion, anxiety sensitivity, and dependency. Extroversion has been negatively associated with agoraphobia, but not panic disorder. Anxiety sensitivity, or a belief that symptoms of anxiety are dangerous, predicts panic disorder and agoraphobia without panic attacks.Dependent and avoidant personality traits can also predict the onset of agoraphobia.